1 /* 2 * jump label support 3 * 4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com> 5 * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com> 6 * 7 */ 8 #include <linux/memory.h> 9 #include <linux/uaccess.h> 10 #include <linux/module.h> 11 #include <linux/list.h> 12 #include <linux/slab.h> 13 #include <linux/sort.h> 14 #include <linux/err.h> 15 #include <linux/static_key.h> 16 #include <linux/jump_label_ratelimit.h> 17 18 #ifdef HAVE_JUMP_LABEL 19 20 /* mutex to protect coming/going of the the jump_label table */ 21 static DEFINE_MUTEX(jump_label_mutex); 22 23 void jump_label_lock(void) 24 { 25 mutex_lock(&jump_label_mutex); 26 } 27 28 void jump_label_unlock(void) 29 { 30 mutex_unlock(&jump_label_mutex); 31 } 32 33 static int jump_label_cmp(const void *a, const void *b) 34 { 35 const struct jump_entry *jea = a; 36 const struct jump_entry *jeb = b; 37 38 if (jea->key < jeb->key) 39 return -1; 40 41 if (jea->key > jeb->key) 42 return 1; 43 44 return 0; 45 } 46 47 static void 48 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop) 49 { 50 unsigned long size; 51 52 size = (((unsigned long)stop - (unsigned long)start) 53 / sizeof(struct jump_entry)); 54 sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL); 55 } 56 57 static void jump_label_update(struct static_key *key, int enable); 58 59 void static_key_slow_inc(struct static_key *key) 60 { 61 if (atomic_inc_not_zero(&key->enabled)) 62 return; 63 64 jump_label_lock(); 65 if (atomic_read(&key->enabled) == 0) { 66 if (!jump_label_get_branch_default(key)) 67 jump_label_update(key, JUMP_LABEL_ENABLE); 68 else 69 jump_label_update(key, JUMP_LABEL_DISABLE); 70 } 71 atomic_inc(&key->enabled); 72 jump_label_unlock(); 73 } 74 EXPORT_SYMBOL_GPL(static_key_slow_inc); 75 76 static void __static_key_slow_dec(struct static_key *key, 77 unsigned long rate_limit, struct delayed_work *work) 78 { 79 if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) { 80 WARN(atomic_read(&key->enabled) < 0, 81 "jump label: negative count!\n"); 82 return; 83 } 84 85 if (rate_limit) { 86 atomic_inc(&key->enabled); 87 schedule_delayed_work(work, rate_limit); 88 } else { 89 if (!jump_label_get_branch_default(key)) 90 jump_label_update(key, JUMP_LABEL_DISABLE); 91 else 92 jump_label_update(key, JUMP_LABEL_ENABLE); 93 } 94 jump_label_unlock(); 95 } 96 97 static void jump_label_update_timeout(struct work_struct *work) 98 { 99 struct static_key_deferred *key = 100 container_of(work, struct static_key_deferred, work.work); 101 __static_key_slow_dec(&key->key, 0, NULL); 102 } 103 104 void static_key_slow_dec(struct static_key *key) 105 { 106 __static_key_slow_dec(key, 0, NULL); 107 } 108 EXPORT_SYMBOL_GPL(static_key_slow_dec); 109 110 void static_key_slow_dec_deferred(struct static_key_deferred *key) 111 { 112 __static_key_slow_dec(&key->key, key->timeout, &key->work); 113 } 114 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred); 115 116 void jump_label_rate_limit(struct static_key_deferred *key, 117 unsigned long rl) 118 { 119 key->timeout = rl; 120 INIT_DELAYED_WORK(&key->work, jump_label_update_timeout); 121 } 122 EXPORT_SYMBOL_GPL(jump_label_rate_limit); 123 124 static int addr_conflict(struct jump_entry *entry, void *start, void *end) 125 { 126 if (entry->code <= (unsigned long)end && 127 entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start) 128 return 1; 129 130 return 0; 131 } 132 133 static int __jump_label_text_reserved(struct jump_entry *iter_start, 134 struct jump_entry *iter_stop, void *start, void *end) 135 { 136 struct jump_entry *iter; 137 138 iter = iter_start; 139 while (iter < iter_stop) { 140 if (addr_conflict(iter, start, end)) 141 return 1; 142 iter++; 143 } 144 145 return 0; 146 } 147 148 /* 149 * Update code which is definitely not currently executing. 150 * Architectures which need heavyweight synchronization to modify 151 * running code can override this to make the non-live update case 152 * cheaper. 153 */ 154 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry, 155 enum jump_label_type type) 156 { 157 arch_jump_label_transform(entry, type); 158 } 159 160 static void __jump_label_update(struct static_key *key, 161 struct jump_entry *entry, 162 struct jump_entry *stop, int enable) 163 { 164 for (; (entry < stop) && 165 (entry->key == (jump_label_t)(unsigned long)key); 166 entry++) { 167 /* 168 * entry->code set to 0 invalidates module init text sections 169 * kernel_text_address() verifies we are not in core kernel 170 * init code, see jump_label_invalidate_module_init(). 171 */ 172 if (entry->code && kernel_text_address(entry->code)) 173 arch_jump_label_transform(entry, enable); 174 } 175 } 176 177 static enum jump_label_type jump_label_type(struct static_key *key) 178 { 179 bool true_branch = jump_label_get_branch_default(key); 180 bool state = static_key_enabled(key); 181 182 if ((!true_branch && state) || (true_branch && !state)) 183 return JUMP_LABEL_ENABLE; 184 185 return JUMP_LABEL_DISABLE; 186 } 187 188 void __init jump_label_init(void) 189 { 190 struct jump_entry *iter_start = __start___jump_table; 191 struct jump_entry *iter_stop = __stop___jump_table; 192 struct static_key *key = NULL; 193 struct jump_entry *iter; 194 195 jump_label_lock(); 196 jump_label_sort_entries(iter_start, iter_stop); 197 198 for (iter = iter_start; iter < iter_stop; iter++) { 199 struct static_key *iterk; 200 201 iterk = (struct static_key *)(unsigned long)iter->key; 202 arch_jump_label_transform_static(iter, jump_label_type(iterk)); 203 if (iterk == key) 204 continue; 205 206 key = iterk; 207 /* 208 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. 209 */ 210 *((unsigned long *)&key->entries) += (unsigned long)iter; 211 #ifdef CONFIG_MODULES 212 key->next = NULL; 213 #endif 214 } 215 jump_label_unlock(); 216 } 217 218 #ifdef CONFIG_MODULES 219 220 struct static_key_mod { 221 struct static_key_mod *next; 222 struct jump_entry *entries; 223 struct module *mod; 224 }; 225 226 static int __jump_label_mod_text_reserved(void *start, void *end) 227 { 228 struct module *mod; 229 230 mod = __module_text_address((unsigned long)start); 231 if (!mod) 232 return 0; 233 234 WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod); 235 236 return __jump_label_text_reserved(mod->jump_entries, 237 mod->jump_entries + mod->num_jump_entries, 238 start, end); 239 } 240 241 static void __jump_label_mod_update(struct static_key *key, int enable) 242 { 243 struct static_key_mod *mod = key->next; 244 245 while (mod) { 246 struct module *m = mod->mod; 247 248 __jump_label_update(key, mod->entries, 249 m->jump_entries + m->num_jump_entries, 250 enable); 251 mod = mod->next; 252 } 253 } 254 255 /*** 256 * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop() 257 * @mod: module to patch 258 * 259 * Allow for run-time selection of the optimal nops. Before the module 260 * loads patch these with arch_get_jump_label_nop(), which is specified by 261 * the arch specific jump label code. 262 */ 263 void jump_label_apply_nops(struct module *mod) 264 { 265 struct jump_entry *iter_start = mod->jump_entries; 266 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 267 struct jump_entry *iter; 268 269 /* if the module doesn't have jump label entries, just return */ 270 if (iter_start == iter_stop) 271 return; 272 273 for (iter = iter_start; iter < iter_stop; iter++) { 274 arch_jump_label_transform_static(iter, JUMP_LABEL_DISABLE); 275 } 276 } 277 278 static int jump_label_add_module(struct module *mod) 279 { 280 struct jump_entry *iter_start = mod->jump_entries; 281 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 282 struct jump_entry *iter; 283 struct static_key *key = NULL; 284 struct static_key_mod *jlm; 285 286 /* if the module doesn't have jump label entries, just return */ 287 if (iter_start == iter_stop) 288 return 0; 289 290 jump_label_sort_entries(iter_start, iter_stop); 291 292 for (iter = iter_start; iter < iter_stop; iter++) { 293 struct static_key *iterk; 294 295 iterk = (struct static_key *)(unsigned long)iter->key; 296 if (iterk == key) 297 continue; 298 299 key = iterk; 300 if (__module_address(iter->key) == mod) { 301 /* 302 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH. 303 */ 304 *((unsigned long *)&key->entries) += (unsigned long)iter; 305 key->next = NULL; 306 continue; 307 } 308 jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL); 309 if (!jlm) 310 return -ENOMEM; 311 jlm->mod = mod; 312 jlm->entries = iter; 313 jlm->next = key->next; 314 key->next = jlm; 315 316 if (jump_label_type(key) == JUMP_LABEL_ENABLE) 317 __jump_label_update(key, iter, iter_stop, JUMP_LABEL_ENABLE); 318 } 319 320 return 0; 321 } 322 323 static void jump_label_del_module(struct module *mod) 324 { 325 struct jump_entry *iter_start = mod->jump_entries; 326 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 327 struct jump_entry *iter; 328 struct static_key *key = NULL; 329 struct static_key_mod *jlm, **prev; 330 331 for (iter = iter_start; iter < iter_stop; iter++) { 332 if (iter->key == (jump_label_t)(unsigned long)key) 333 continue; 334 335 key = (struct static_key *)(unsigned long)iter->key; 336 337 if (__module_address(iter->key) == mod) 338 continue; 339 340 prev = &key->next; 341 jlm = key->next; 342 343 while (jlm && jlm->mod != mod) { 344 prev = &jlm->next; 345 jlm = jlm->next; 346 } 347 348 if (jlm) { 349 *prev = jlm->next; 350 kfree(jlm); 351 } 352 } 353 } 354 355 static void jump_label_invalidate_module_init(struct module *mod) 356 { 357 struct jump_entry *iter_start = mod->jump_entries; 358 struct jump_entry *iter_stop = iter_start + mod->num_jump_entries; 359 struct jump_entry *iter; 360 361 for (iter = iter_start; iter < iter_stop; iter++) { 362 if (within_module_init(iter->code, mod)) 363 iter->code = 0; 364 } 365 } 366 367 static int 368 jump_label_module_notify(struct notifier_block *self, unsigned long val, 369 void *data) 370 { 371 struct module *mod = data; 372 int ret = 0; 373 374 switch (val) { 375 case MODULE_STATE_COMING: 376 jump_label_lock(); 377 ret = jump_label_add_module(mod); 378 if (ret) 379 jump_label_del_module(mod); 380 jump_label_unlock(); 381 break; 382 case MODULE_STATE_GOING: 383 jump_label_lock(); 384 jump_label_del_module(mod); 385 jump_label_unlock(); 386 break; 387 case MODULE_STATE_LIVE: 388 jump_label_lock(); 389 jump_label_invalidate_module_init(mod); 390 jump_label_unlock(); 391 break; 392 } 393 394 return notifier_from_errno(ret); 395 } 396 397 struct notifier_block jump_label_module_nb = { 398 .notifier_call = jump_label_module_notify, 399 .priority = 1, /* higher than tracepoints */ 400 }; 401 402 static __init int jump_label_init_module(void) 403 { 404 return register_module_notifier(&jump_label_module_nb); 405 } 406 early_initcall(jump_label_init_module); 407 408 #endif /* CONFIG_MODULES */ 409 410 /*** 411 * jump_label_text_reserved - check if addr range is reserved 412 * @start: start text addr 413 * @end: end text addr 414 * 415 * checks if the text addr located between @start and @end 416 * overlaps with any of the jump label patch addresses. Code 417 * that wants to modify kernel text should first verify that 418 * it does not overlap with any of the jump label addresses. 419 * Caller must hold jump_label_mutex. 420 * 421 * returns 1 if there is an overlap, 0 otherwise 422 */ 423 int jump_label_text_reserved(void *start, void *end) 424 { 425 int ret = __jump_label_text_reserved(__start___jump_table, 426 __stop___jump_table, start, end); 427 428 if (ret) 429 return ret; 430 431 #ifdef CONFIG_MODULES 432 ret = __jump_label_mod_text_reserved(start, end); 433 #endif 434 return ret; 435 } 436 437 static void jump_label_update(struct static_key *key, int enable) 438 { 439 struct jump_entry *stop = __stop___jump_table; 440 struct jump_entry *entry = jump_label_get_entries(key); 441 442 #ifdef CONFIG_MODULES 443 struct module *mod = __module_address((unsigned long)key); 444 445 __jump_label_mod_update(key, enable); 446 447 if (mod) 448 stop = mod->jump_entries + mod->num_jump_entries; 449 #endif 450 /* if there are no users, entry can be NULL */ 451 if (entry) 452 __jump_label_update(key, entry, stop, enable); 453 } 454 455 #endif 456